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Scientific article
English

Configurationally Stable Doubly Bridged Biphenyl Azocines through Copper-Catalyzed Double Carbene Insertions into the Corresponding Azepines

Published inSynthesis, vol. 48, no. 19, p. 3254-3262
Publication date2016
Abstract

Doubly bridged biphenyl azocines can be prepared in a single step through copper-catalyzed reactions of a doubly bridged biphenyl azepine and diazodiester reagents. Double [1,2]-Stevens rearrangements occur at 100 °C to afford doubly tethered eight-membered rings (49 to 61%) as trans and cis regioisomers (1:1 ratio). These products present an axial chirality. ECD and VCD analyses of the separated enantiomers (CSP-HPLC) were used to assign the absolute configuration. High configurational stability is observed for both regioisomers as racemization does not occur after 1 week of heating at 208 °C in dodecane (ΔG ‡ > 41 kcal·mol–1). Interestingly, reactions performed at 40 °C retain a certain level of enantiospecificity (82–86%), avoiding, for the most part, thermal racemization of the starting material.

Keywords
  • Azepine
  • Azocine
  • Carbenes
  • Configurational stability
  • [1,2]-Stevens rearrangement
  • Ylides
Citation (ISO format)
HARTHONG, Steven et al. Configurationally Stable Doubly Bridged Biphenyl Azocines through Copper-Catalyzed Double Carbene Insertions into the Corresponding Azepines. In: Synthesis, 2016, vol. 48, n° 19, p. 3254–3262. doi: 10.1055/s-0035-1562467
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ISSN of the journal0039-7881
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